Science

Fukushima: The true aftermath

October 24 2011

Rebecca Saunders looks at the management and human repercussions of the disaster

It has come to light that more than 300,000 children living near to the Fukushima nuclear power station will be checked for thyroid abnormalities.

Japanese authorities have said that the results of the checks will not be published, adding further fuel to the argument by the residents of Fukushima and the surrounding area, that they are being kept in the dark about the dangerous after-effects of the nuclear meltdown.

Seven months ago, on the 11th March 2011, at 2145 Pacific Standard Time, a magnitude 9.0 earthquake shook Honshu, the main island of Japan. Such was the enormity of the earthquake that it moved the island 8ft to the East and shifted the earth by an estimated 25cm on its axis.

The tsunami wave that was triggered swept six miles inland at a height reaching 133ft. It also flooded Fukushima power station which was operating three out of six reactors on the day of the quake, cutting off power supply to the vital cooling pumps that would have been able to prevent the nuclear melt-down that followed. An evacuation zone was instantly put in place 10km around the plant, which within days was increased to 20km.

Radiation levels rocketed and not even the plant’s operators Tokyo Electric Power Company (TEPCO) could sweep the nuclear fall-out under the proverbial carpet.

Radiation is measured by sevierts (usually given in milli-sevierts, mSv) which measure the absorbed dose of radiation, whereas becquerels are a measurement of the rate of emission at source of the radioactivity. With varying numbers being released by the Japanese authorities with very little explanation, the general public began to panic and wanted to know what the danger truly was.

The day after the tsunami, levels of radiation hit 1.577 millisevierts per hour around the plant, about the same as would have been allowed in one year normally. Not instantly harmful, but over the course of a year an individual would receive a cumulative dose of 575mSv; enough to seriously increase your risk of cancer.

However, within a few days the figure had risen to nearly 400mSv per hour being kicked out of Fukushima proving enough to provoke the early stages of radiation sickness with several workers falling ill.

Information being given to the evacuees was still limited and the Japanese press reports gave mixed messages about just how much radiation residents were being exposed to. Now, the estimates are that the disaster has so far released over 500,000 terabecquerels of radioactive particles.

Japan has worked hard to rebuild after the earthquake and tsunami, but the lasting effects of the nuclear fall-out that followed are harder to get rid of.

Health-risks are often talked about in conjunction with exposure to radiation, but how much is too much and what will it do?  Radioactive particles emit radiation as they decay, this radiation is different from that associated with UV, microwave or radio-waves because it is ionising. As this radiation hits human tissue it reverberates around the cell causing damage at a molecular level to structural elements of the cell, and more importantly to its DNA by breaking chemical bonds.

Our cells are able to repair damaged DNA but when a lot of damage has occurred, this isn’t always possible leaving sometimes fatal effects (in the case of high-doses) and causing the cell to die or potentially cancerous mutations (at lower doses).

The radiation damage may just pre-dispose a cell to become a cancer cell by mutating the DNA which doesn’t immediately induce cancerous replication but may contribute to the formation of cancer later on in life due to the mutation being copied in duplicate cells.

Alternatively, the damage may be so irreparable that multiple cellular processes are stopped including the ability to prevent the cell from replicating – leading to a cancerous tumour.

However, it’s not just cancer that can be caused by radiation, other disorders and diseases stemming from mutated DNA can be prompted.  The damage caused to DNA can be passed on not just to duplicated cells within the body, but also to potential offspring where it can cause deformities or learning difficulties in future generations.

Relating this to Fukushima, 400mSv isn’t enough to induce full-blown radiation sickness but could cause damage to the DNA leading to an increase in an adult’s chance of developing cancer by 2-4%.  It must be noted that this dose was actually an hourly dose in the days after the meltdown. By the time that the hourly dose reached this level, most of the surrounding 20km had been evacuated although just outside of the exclusion zone measurements of up to 100mSv per hour were being recorded.

According to the World Nuclear Association, 100mSv per year is the “lowest level at which any increase in cancer is clearly evident, above this, the probability of cancer occurrence (rather than the severity) is assumed to increase with dose.”

However, exposing children to this dose can pose a much greater risk as a child’s cells duplicate quicker as they grow – amplifying any potential mutation. The thyroid gland is particularly sensitive as it usually concentrates iodine in our diet to produce important hormones needed for the body to function properly.

One of the most abundant radioactive isotopes is that of iodine and so when exposed to this, the thyroid concentrates and holds onto it, increasing the chances of cancer forming as well as other thyroid disorders.

Since Chernobyl, more than 6,000 cases (in 2005) of thyroid cancer had been reported in those who had been children and adolescents at the time of exposure, several thousand more suffer from thyroid disorders such as hyper-thyroidism or thyroid nodules.

The issue surrounding irradiated food is contentious. The small amounts of radio-activity found in some of the food produced around the exclusion zone and the tap water circulating in the province is not enough to pose a threat for someone never exposed to the initial dose of radiation if not consumed regularly.

It is probably good to be cautious, but the Japanese government haven’t fully explained the reason for their caution and so add to the hysteria surrounding the original disaster. The whole event has shown the need for clear and understandable explanation of health-risks surrounding events such as this, to minimise panic, reduce confusion and improve access to necessary care for those truly affected.

TEPCO have been heavily criticised in the months following the disaster due to the way they handled the emergency cooling of the reactors resulting in vast radio-active leaks not only into the air but also the soil and sea.

Warnings given to the company when they built the power station included concerns over the low-lying nature of the emergency power generators and pump equipment which could well have prevented the melt-down if they hadn’t been engulfed by the tsunami.

The nuclear fall-out displaced 50,000 households and has removed the livelihoods of thousands more as farmers and fishermen now no longer have viable stock to sell as radiation levels found within the food are considered too high.

Only time will tell as to how much the radiation exposure of the residents from the surrounding area will affect their health.  For scientists, it will provide an interesting study into the effects of radiation to compare with data collected since Chernobyl.

For countries around the world, the Fukushima nuclear disaster has highlighted the dangers of nuclear power, for some it has been enough to put the brakes on plans for their own countries, for others it has been dismissed as a natural disaster.

For those evacuated, it comes down to, quite simply, the ongoing need to ensure their family’s safety. in the coming months and years.

 

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